Bag of little isopod shaped robots. They are fast moving with nuclear batteries and tungsten carbide shells and lots of sharp edges for chewing and burrowing through flesh. They can also dig into the ground a few inches and hibernate like cicadas to protect an area. Not wireless networked but instead have onboard processing for voice commands, use sense of smell for IFF and echolocation to coordinate their swarming.

Couldn’t stop a gun, but they are a deterrent against using it because if you shoot me we both die but you die in a more horrible way.